package com.thx.common.web.util;

import org.apache.commons.codec.binary.Base64;
import org.springframework.util.Assert;

import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Http与Servlet工具类.
 *
 * @author calvin
 */
public class ServletUtils {

  //-- Content Type 定义 --//
  public static final String TEXT_TYPE = "text/plain";
  public static final String JSON_TYPE = "application/json";
  public static final String XML_TYPE = "text/xml";
  public static final String HTML_TYPE = "text/html";
  public static final String JS_TYPE = "text/javascript";
  public static final String EXCEL_TYPE = "application/vnd.ms-excel";

  //-- Header 定义 --//
  public static final String AUTHENTICATION_HEADER = "Authorization";

  //-- 常用数值定义 --//
  public static final long ONE_YEAR_SECONDS = 60 * 60 * 24 * 365;

  /**
   * 设置客户端缓存过期时间 的Header.
   */
  public static void setExpiresHeader(HttpServletResponse response, long expiresSeconds) {
    //Http 1.0 header
    response.setDateHeader("Expires", System.currentTimeMillis() + expiresSeconds * 1000);
    //Http 1.1 header
    response.setHeader("Cache-Control", "private, max-age=" + expiresSeconds);
  }

  /**
   * 设置禁止客户端缓存的Header.
   */
  public static void setDisableCacheHeader(HttpServletResponse response) {
    //Http 1.0 header
    response.setDateHeader("Expires", 1L);
    response.addHeader("Pragma", "no-cache");
    //Http 1.1 header
    response.setHeader("Cache-Control", "no-cache, no-store, max-age=0");
  }

  /**
   * 设置LastModified Header.
   */
  public static void setLastModifiedHeader(HttpServletResponse response, long lastModifiedDate) {
    response.setDateHeader("Last-Modified", lastModifiedDate);
  }

  /**
   * 设置Etag Header.
   */
  public static void setEtag(HttpServletResponse response, String etag) {
    response.setHeader("ETag", etag);
  }

  /**
   * 根据浏览器If-Modified-Since Header, 计算文件是否已被修改.
   * 如果无修改, checkIfModify返回false ,设置304 not modify status.
   *
   * @param lastModified 内容的最后修改时间.
   */
  public static boolean checkIfModifiedSince(
      HttpServletRequest request, HttpServletResponse response, long lastModified) {
    long ifModifiedSince = request.getDateHeader("If-Modified-Since");
    if ((ifModifiedSince != -1) && (lastModified < ifModifiedSince + 1000)) {
      response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
      return false;
    }
    return true;
  }

  /**
   * 根据浏览器 If-None-Match Header, 计算Etag是否已无效.
   * 如果Etag有效, checkIfNoneMatch返回false, 设置304 not modify status.
   *
   * @param etag 内容的ETag.
   */
  public static boolean checkIfNoneMatchEtag(
      HttpServletRequest request, HttpServletResponse response, String etag) {
    String headerValue = request.getHeader("If-None-Match");
    if (headerValue != null) {
      boolean conditionSatisfied = false;
      if (!"*".equals(headerValue)) {
        StringTokenizer commaTokenizer = new StringTokenizer(headerValue, ",");

        while (!conditionSatisfied && commaTokenizer.hasMoreTokens()) {
          String currentToken = commaTokenizer.nextToken();
          if (currentToken.trim().equals(etag)) {
            conditionSatisfied = true;
          }
        }
      } else {
        conditionSatisfied = true;
      }

      if (conditionSatisfied) {
        response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
        response.setHeader("ETag", etag);
        return false;
      }
    }
    return true;
  }

  /**
   * 设置让浏览器弹出下载对话框的Header.
   *
   * @param fileName 下载后的文件名.
   */
  public static void setFileDownloadHeader(HttpServletResponse response, String fileName) {
    try {
      //中文文件名支持
      String encodedfileName = new String(fileName.getBytes(), "ISO8859-1");
      response.setHeader("Content-Disposition", "attachment; filename=\"" + encodedfileName + "\"");
    } catch (UnsupportedEncodingException ex) {
      // 如果不支持该编码, 那真的不可能
      response.setHeader("Content-Disposition", "attachment; filename=\"attachment\"");
    }
  }

  /**
   * 取得带相同前缀的Request Parameters.
   * 返回的结果的Parameter名已去除前缀.
   */
  @SuppressWarnings("unchecked")
  public static Map<String, Object> getParametersStartingWith(
      ServletRequest request, String prefix) {
    Assert.notNull(request, "Request must not be null");
    Enumeration paramNames = request.getParameterNames();
    Map<String, Object> params = new TreeMap<String, Object>();
    if (prefix == null) {
      prefix = "";
    }
    while (paramNames != null && paramNames.hasMoreElements()) {
      String paramName = (String) paramNames.nextElement();
      if ("".equals(prefix) || paramName.startsWith(prefix)) {
        String unprefixed = paramName.substring(prefix.length());
        String[] values = request.getParameterValues(paramName);
        if (values == null || values.length == 0) {
          // Do nothing, no values found at all.
        } else if (values.length > 1) {
          params.put(unprefixed, values);
        } else {
          params.put(unprefixed, values[0]);
        }
      }
    }
    return params;
  }

  /**
   * 对Http Basic验证的 Header进行编码.
   */
  public static String encodeHttpBasic(String userName, String password) {
    String encode = userName + ":" + password;
    return "Basic " + new String(Base64.encodeBase64(encode.getBytes()));
  }
}
